The present invention relates to a method for cleaning cylinders of rotary printing presses. A cleaning cloth is pulled off a supply roll located in a first receiving device, is pressed against the surface of the cylinder to be cleaned during the cleaning process by a pressing element, and is collected in a second receiving device in the form of a receiving roll. The supply roll is replaced by a fresh supply roll after the cleaning cloth on the supply roll has been used up and the full receiving roll is also removed. The present invention also relates to a device for cleaning cylinders of rotary printing presses. The device consists of a first cleaning cloth depot, to which a supply roll and a spindle are allocated, a second cleaning cloth depot, to which a receiving roll and a spindle are allocated, a pressure element for pressing a cleaning cloth against the cylinder to be cleaned, and a single drive motor, whose direction of rotation can be reversed, for driving both spindles.
For replacing a used-up supply roll of a cleaning cloth in a printing press, it is customary to first remove the empty spindle of the supply roll from the cleaning device. A fresh cleaning cloth is then wound on the spindle and it is put back. The full receiving roll is removed, the soiled cleaning cloth is unwound from it, the empty spindle is again placed into the cleaning device and the beginning of the cleaning cloth is fixed in place on the now empty spindle.
There has been no lack of attempts to make this method more user-friendly. One prior solution is known from DE 38 41 269 A1, wherein the soiled cleaning cloth is wound back on the supply spindle, so that the supply roller can then be replaced by a fresh one. A single motor is provided for this purpose and which, depending on its direction of rotation, drives one or the other of the spindles.
A solution for rewinding the soiled cleaning cloth is known from EP 0 520 521 A1. Here, a drive motor is employed, which can be driven in one direction and which is connected with a transfer mechanism. This transfer mechanism is equipped for selectively coupling the motor with the rollers for rotation in the direction of rotation of the receiving roller; i.e. during cleaning operations or for rotation in the other direction, for rewinding the soiled cleaning cloth.
In the solution known from DE 43 19 258 A1, rewinding is avoided. In this prior art device, the cleaning device is designed in such a way that it can be rotated around its longitudinal axis by approximately 180xc2x0. The positions of both rolls can then be reversed after the cleaning cloth has been wound off the supply roll. The now empty supply roll is used for winding up the soiled cleaning cloth, i.e. as a receiving roll. The full receiving roll with the soiled cleaning cloth can then be removed and provides space for a fresh supply cloth.
A further solution for simplifying the changing of the cleaning cloth is known from DE 195 43 518 A1. The design of this prior device is such that the cleaning cloth of both rolls is wound on tubes, which in turn are seated on shafts seated laterally in the machine frame. Because of this, it is possible to remove the rollers from the machine transversely and parallel with the cylinder axis and in this way to replace the empty roller by a fresh one.
The limitations of the prior art devices include the fact that no exact information regarding the length of the cleaning cloth is available when placing such a fresh roll of cleaning cloth in the device. It is possible to determine the length of the cleaning cloth during the preparation of the roll, i.e. when winding the cleaning cloth onto the spindle. However, large deviations sometimes occur, which deviations are caused, in particular, by errors caused by the operators.
The determination and entry of cleaning cloth length values into a computer is also cumbersome, and furthermore the effective length sometimes changes considerably during the cleaning process because of cloth stretching and from other process-related effects. Therefore, an exact prediction of the time when the end of the cleaning cloth will be reached, and process values connected therewith, is not possible. Mechanical scanning of the diameter of the roll, such as is presently performed, as a rule is too inexact for sufficiently predicting the end of the cleaning cloth.
It is the object of the present invention to provide a method and a device, by which the cleaning cloth change is simplified and with which it is possible, in the course of changing the cleaning cloths, to determine the exact effective length of the cleaning cloth available for the cleaning process with little effort.
This object is attained by the placement of a fresh supply roll of a cleaning cloth in a storage area for soiled cleaning cloths. The fresh cleaning cloth is wound off the soiled storage spindle onto a clean storage area spindle. During this winding, the length of the clean cloth is measured. An end of the fresh cleaning cloth stays in the soiled storage area and forms the start of the receiving roll of soiled cleaning cloth.
The advantage of the attainment of the object of the present invention lies in that the effective length of the cleaning cloth can now be accurately determined, so that data is made available for controlling the actual cleaning process, which makes it possible to automate this process. Moreover, the soiled cleaning cloth need not be rewound, so that no further soiling of the cleaning device occurs.